1. Field of the Invention
The present invention relates to a chip-component structure including a multilayer capacitor and an interposer to be mounted on a circuit board with the capacitor being disposed thereon.
2. Description of the Related Art
Currently, chip components, especially, small multilayer capacitors are frequently used in circuit boards of mobile terminals such as cellular phones. A typical multilayer capacitor includes a laminated body shaped like a substantially rectangular parallelepiped in which internal electrodes are provided between a plurality of dielectric layers, and outer electrodes provided on end surfaces of the laminated body opposite to each other in a longitudinal direction.
In general, the multilayer capacitor is electrically and physically connected to a circuit board by placing the outer electrodes on mounting lands of the circuit board and joining the mounting lands and the outer electrodes with a joining material such as solder (for example, see Japanese Unexamined Patent Application Publication No. 8-55752).
In such a multilayer capacitor, small mechanical distortions are sometimes caused by the application of voltage. When the distortions are transmitted to the circuit board, acoustic noise is produced by the circuit board. To address this problem, the capacitor is sometimes mounted on the circuit board with another member being disposed therebetween (for example, see Japanese Unexamined Patent Application Publication Nos. 2004-134430 and 2010-123614). An interposer or a conductive support member is used, for example, as the member to be disposed between the capacitor and the circuit board.
An interposer is a substrate including an upper electrode to which the outer electrodes of the multilayer capacitor are joined, a lower electrode to be joined to the mounting lands of the circuit board, and side electrodes provided on end surfaces of the interposer to connect the upper electrode and the lower electrode.
A conductive support member includes a pair of support legs to be joined at lower ends to the mounting lands of the circuit board, and the support legs clamp and support the multilayer capacitor in the air.
In general, there is a demand that the multilayer capacitor has a low equivalent series inductance (ESL). However, when the multilayer capacitor is mounted on a circuit board with the interposer being disposed therebetween, a current path is extended by wiring provided in the interposer, and this increases ESL.
To reduce ESL increased by the wiring in the interposer, it is effective to increase the cross-sectional area of the wiring by increasing the width of side electrodes. However, if the width of the side electrodes is increased, the amount of joining material that wets and spreads upward on the side electrodes increases, and the joining material easily reaches outer electrodes of the capacitor. Consequently, distortion of the capacitor is likely to be transmitted to the circuit board via the joining material such that acoustic noise is likely to be produced from the circuit board.